Portability is an increasingly important radiotelephone feature for consumers; therefore, radiotelephones are being designed and produced to be as small as possible. A common problem with small phones is that when a user holds a phone to his or her ear during use, the microphone is positioned far from the user's mouth, resulting is poor sound transmission. With an emphasis on miniaturization, numerous phones on the market now have a member which is compactly stowed against the phone's main body until a user extends the member. These extending members either rotate or slide out from the main body and are designed to enhance a phone's acoustical performance.
Many phones containing a microphone in the main body have an extending member that contains no electronics but merely acts as a surface which reflects a user's voice into the microphone when the member is extended and the phone is held to the user's ear. An example of such a radiotelephone is the model DH 338 manufactured by Ericsson Inc. Some extending members contain microphones such that when the member is extended, and the phone is held to a user's ear, the microphone is positioned near the user's mouth. The radiotelephone described in U.S. Pat. No. 4,845,772 to Metroka et al. contains a microphone in the extending member. Another type of extending member contains no electronics but does contain an acoustic duct which has an inlet that opens near a user's mouth and an outlet which opens into an aperture in the main body of the phone. The aperture in the phone leads directly to a microphone. When in use, acoustic ducts carry sound from the source to the microphone, dramatically improving sound quality and requiring no electronic parts.
At least two types of extending members with acoustic ducts are known, both of which are hinged to a phone and rotate about the hinge to an extended position for use. The first type described in European Pat. No. 275,996 B1 has an acoustic duct which opens in alignment with an opening in the main body only when the member is rotated out to its extended position. A tight fit between the extending member opening and the main body opening is required to maximize sound transmission. The second type embodied in Ericsson's model number AF 738 has an acoustic duct which leads through the hinge of the phone and opens in alignment with the member's axis of rotation and with an opening in the main body. Two arms of the hinge apply constant force to keep the opening of the extending member tightly abutting the opening of the main body.
All of the extending members described above have undesirable attributes. Firstly, although the extending member for voice reflection is inexpensive, easy to assemble, and easy to replace, it often does not reflect enough of the user's voice to adequately enhance sound quality. Secondly, when the extending member contains a microphone, there must be an electrical connection to the main body that must withstand repeated movement of the extending member. Phones of this type use expensive parts, are likely to break when dropped, and are difficult to assemble and repair. Thirdly, the extending members with acoustic ducts as mentioned above are prone to wear and either lose sound through leaks between the openings in the extending member and the main body, or they require a number of expensive, complicated sealing parts that are difficult to assemble.
Thus, small, portable radiotelephones are in need of extending members that are inexpensive, easy to assemble and replace, durable to repeated extensions, robust, and reliable while providing excellent acoustical performance.